Field of the Invention
The present invention relates to a liquid discharge device, and particularly relates to a liquid discharge device including a circulation channel that circulates in an ejection unit and storage unit of liquid.
Description of the Related Art
Recently, a demand for printing with a small number of copies has grown in the printing industry. Since it is necessary to make a plate in offset printing, there is a problem in respect of time and costs when printing with a small number of copies is performed. Therefore, inkjet recording of a single-pass system is suitably used.
However, in the single pass system, there is a fault that, when a nozzle that does not perform ejection or a nozzle with ejection bending exists, a stripe is remarkable in the lack part. As a factor to cause the stripe, air bubbles mixed in a head (the rise of a dissolved oxygen amount) are a large factor. By installing a deaeration module in a circuit to remove the air bubbles, the dissolved oxygen amount in ink is kept at a low level during circulation by the deaeration module. However, ink that is not deaerated is supplemented when ink that has been deaerated is consumed by printing, and ink with a large dissolved oxygen amount is ejected because the ink that is not deaerated is supplied into the head, which leads to the degradation of printing quality.
Normally, ink in a buffer tank circulates in the buffer tank, a deaeration module and an ejection head, and keeps a dissolved oxygen amount at about 10%. Since the ink is discharged from the ejection head at printing, the ink in the buffer tank decreases and new ink is refilled from a main tank, but the refilled ink is not deaerated and ink with a dissolved oxygen amount of about 80% is refilled. When ink is not sufficiently diffused in the buffer tank and is supplied to the ejection head, since ink with a high dissolved oxygen amount is ejected, it leads to the degradation of printing quality.
To suppress the dissolved oxygen amount of ink during printing, Japanese Patent Application Laid-Open No. 11-198393 (PTL 1) defines a configuration in which ink in a sub-tank is stirred by providing a partition wall such that the ink flows in the sub-tank in a meandering manner in an ink supply device that supplies the ink from a main tank to the sub-tank and supplies the ink from the sub-tank to a printing head. Moreover, Japanese Patent Application Laid-Open No. 2010-184424 (PTL 2) describes providing stir means in a sub-tank provided between an ink tank and a printing head and stirring ink in the sub-tank.